This disclosure relates generally to the field of image processing, and more particularly to a system and a method for residual analysis of images.
In many conventional image processing scenarios comprising hyperspectral imaging (HSI) systems, hyperspectral sensors collect data of an image from one spatial line and disperse the spectrum across a perpendicular direction of the focal plane of the optics receiving the image. Thus a focal plane pixel measures the intensity of a given spot on the ground in a specific waveband. A complete HSI cube scene is formed by scanning this spatial line across the scene that is imaged. The complete HSI cube may be analyzed as a measurement of the spectrum, the intensity in many wavebands, for a spatial pixel. This spatial pixel represents a given spot on the ground in a cross-scan direction for one of the lines at a given time in the scan direction. These spectra are analyzed to detect targets or spectral anomalies.
Many focal plane arrays (FPAs) used in HSI systems, especially HgCdTe (or MCT), exhibit pixels with random and unexpected changes in offset that vary with time called “blinker pixels” or simply “blinkers.” A blinker, a 1/f type of noise, is a time-dependent offset as contrasted with a constant offset. A typical blinker associated with HSI data has an offset value for some period of time over which the data is collected and then another offset value for another period of time. The unpredictable change in offset over time wreaks havoc with calibration of HSI system (and components) and corrupts the HSI data. Blinkers negatively impact the probability ratio that a target is declared when it is present relative to the probability that a target is declared when a target is in fact not present (Pd/Pfa), and the operability specifications of MCT detectors. Removing blinker pixels results in holes in the measurements for those frames (scenes) and removal is only moderately successful.
MCT FPAs have many advantages for HSI but they also have blinkers, typically 5-30% in long-wave infrared (LWIR) FPAs. Other FPAs, such as short-wave infrared FPAs, also experience blinkers but to a lesser degree than LWIR FPAs. Stringent customer requirements drive HSI systems toward materials with greater cooling requirements or reduced HgCdTe yields, which are expensive. Improved software mitigation of blinkers (and other time-dependent offsets) can improve product and FPA yield/cost. Accordingly, there is a need for on-platform scene based non-uniformity correction of pixels in an inexpensive and computationally fast manner.